1. Field of Invention
The present invention relates generally to the field of imaging. More particularly, the invention relates to segmenting an object from an image or sequence of images.
2. Background Information
Image-based tracking systems are designed to track an object by the signature of the object within an image that is received by an imaging system. The signature can be from either a grayscale imaging system, such as an IR imaging system, or a color imaging system. Based upon the location, size and shape of the signature in an image or in a sequence of images, a tracking system can determine position, range and other features of the object. For example, imaging systems used in missile-based tracking systems can identify features of an object based upon the object's signature within an image to classify a signature as a target signature, as well as, determine guidance information for guiding a missile.
The process used in imaging systems to extract or separate out a representation of the object from its signature within an image is called segmenting. Pixels of the signature, which actually illustrate features (i.e., edges) of the object, are used in generating a segment that is representative of the object. After a segment or set of pixels representing the object in the image is defined, a variety of features, both statistical and deterministic in nature, can be evaluated in order to determine information about the object from the segment. For example, the signature of an object is initially indicated within an image by any number of detection schemes. Then a subarea of the image containing the indicated signature is processed to define a set of pixels (i.e., segment) representing the object. Subsequently, the features of the segment can be compared to features of known target types to identify whether the object is a target. In addition, tracking information can be determined by the pixel location and size of the segment from the image, or from a sequence of images.
Image processing segmentation can be inaccurate in depicting or representing the features of an object due to clutter, variations or inconsistencies in the signature of the object. Thus, subsequent evaluations for tracking (i.e. distance, position and/or speed of the object) or identification of the object can be erroneous.
Lighting effects (i.e. shadows), atmospheric conditions (i.e., heat waves radiating from the ground), background imagery, foreground imagery and the resolution limits of the imaging system can cause inconsistencies in the signature or, particularly as the object moves, variations in the signature in a sequence of images. If the imaging system of a tracking system is in motion while tracking the object, changes in the aspect angle, depression angle and distance of the target object to the imaging system can vary the signature of an object in a sequence of images and also cause inconsistencies in the signature. In addition, background imagery, foreground imagery and atmospheric conditions can cause clutter in and around a signature.